Seoul, April 3 South Korea's foreign reserves posted their sharpest monthly decline in about a year in March amid a stronger dollar and authorities' efforts to manage exchange rate volatility, the central bank said on Friday.The country's foreign reserves stood at US$423.66 billion as of end-March, down $3.97 billion from a month earlier, according to the data from the Bank of Korea (BOK).It was the sharpest decline since April 2025, when the amount fell by $4.99 billion on-month, reports Yonhap news agency.The reserves had fallen in December for the first time since June and continued to decline through January before…